Oh, No, Purple Glow!

[bgadow]

Correct...oddly, I tried again the next day, starting it off at 6v and no real emission showing so after a minute or so I turned it to the "color" position (which I think is close to 8) and left the room. When I came back, sure enough, the needle was high in the good range and there was a noticeable glow in the neck. When I turn the control from emission down to "test for shorts" one of the lamps glows dimly for a few seconds and then goes out, and I can repeat that. My initial thought was a short, perhaps only showing up after warming, but I can't find one. I did resistance tests with just the filament hooked up and no shorts between any elements. When the tube tester is showing the purple glow and I switch off the grid voltages the glow dissappears. My guess is that the tube has enough vacuum so that the filament will light but is too gassy to work properly. I did not immediatly blame the crt since I saw on a CTC-31 a purple neck glow caused by a defective video amp. That crt was fine. I can't blame the chassis here, though, since I can duplicate the problem with the tester.